Acetonitrile Hydrogenation Reaction On Pt(111) Surface: A Density Function Theory Study

Hydrogenation of acetonitrile to ethyl amines which include ethylamine, diethylamine,triethylamine are widely used in the pharmaceutical, agriculture, textile, rubber, plasticindustries, etc. Therefore it has important industrial application value. The selectivehydrogenation of acetonitrile not only can realize the comprehensive utilization of acetonitrile,but also can actualize the green chemistry and atom economy of the production. However amixture of three amines can only be obtained and the selectivity is very poor. The mechanismof acetonitrile hydrogenation based catalysts is still poorly understood, which may hinder thedevelopment of the selectivity. Nowadays a lot of experimental researches have been done,but very little theoretical research. The catalyst Pt（111） surface has attracted much attentiondue to its higher activity. So Pt（111） surface often be chosen as the catalyst to accelerate thereaction. Therefore, in this work, we have performed a series of theoretical studies on theadsorption properties of acetonitrile on Pt（111） surface and the mechanism of acetonitrilehydrogenation to ethylamine by Density-Functional Theory （DFT）. The main results aresummarized as:（1） All the possible adsorption configurations of acetonitrile on Pt（111） surface wereinvestigated. The calculation results show that the bridge configuration is the most stableadsorbed form. CH₃CN interacts with two adjacent Pt atoms via the C–N bond and forms onePt–N bond and one Pt–C bond. And the C–N axis is almost parallel to the surface. Becausethe electrons transfer occurs from Pt surface to CH₃CN, the C–N bond is activated andelongated.（2） The intermediates on Pt（111） surface were investigated. The calculation resultsshow that the hydrogenation products of N atom are more stable than the hydrogenationproducts of C atom. With the increase of the number of H atoms, the C–C bond is moreelongate and the adsorption energy is smaller. And the adsorption energy of CH₃CH₂NH₂is the smallest.（3） The coadsorption configurations of the intermediates and H atom on Pt（111） surfacewere investigated. The calculation results show that H atoms on the top site and the fcc siteare more stable than on the bridge site and hcp site. So it shows the H atom has fluidity on thesurface, which can be close to the metal surface. The fluidity is conducive to thehydrogenation reaction.（4） The transition states between reactants and products were found and the reactionmechanisms were explored, which extended our theory study. The reaction energy and thereaction energy barrier were calculated. The calculation results show that the reaction route ofCH₃CN hydrogenation to CH₃CH₂NH₂is: CH₃CNâ†'CH₃CNHâ†'CH₃CHNHâ†'CH₃CHNH₂â†'CH₃CH₂NH₂In conclusion, the behavior of acetonitrile molecule adsorption on Pt catalyst and thehydrogenation reaction were systematically studied in this thesis. This basic work will offertheoretical basis for acetonitrile hydrogenation.